In recent years, as an apparatus for performing image formation with high resolution on various types of recording media, inkjet type image recording apparatuses are widely used. Particularly, in some cases where the recording medium is of a flexible material such as cloth, the recording medium is conveyed under a recording head by an endless conveying belt. In this situation, errors in feeding of the recording medium, so-called edgeless printing, oozing ink out of the back, or the like may cause ink jetted from a recording head to adhere to the conveying belt. Accordingly, ink deposited on the conveying belt is transferred to a newly fed recording medium on the conveying belt to cause a problem such as staining of the subsequently led recording medium. Therefore, such an inkjet recording apparatus having a conveying belt is usually provided with a cleaning device for cleaning the conveying belt.
As means for cleaning a conveying belt, there are known recording apparatuses and conveying devices provided with a cleaning device that wipes off unnecessary ink deposited on the conveying belt with a blade wiper and absorbs ink with a liquid absorption material as auxiliary means (for examples, see Patent Documents 1 to 3). However, in these apparatuses, the blade wiper and the liquid absorption material are pressed hard against the conveying belt, which may damage the conveying belt and affect its durability. Further, in the case where ink deposited on the conveying belt dries and becomes fixed on the conveying belt, the ink cannot always be removed enough. Still further, if the belt width is one meter or longer as in the case of a conveying belt used in an inkjet recording apparatus for textile printing on cloth, it is usually difficult to uniformly press the edge of a blade wiper against a conveying belt surface over the entire width of the conveying belt.
Further, another type of cleaning means is disclosed, that is, an image forming apparatus provided with a cleaning device that absorbs and wipes off ink deposited on a conveying belt with a roller or a pad having a high molecular water absorption polymer (for example, see Patent Document 4). In this apparatus, a double structured roller constructed of a high molecular water absorption polymer, which is an ink absorption layer, covered with a nonwoven material, is employed. Particularly, when a pigment ink is used, dye particles in the ink tend to stay in the nonwoven material or in the surface layer of the high molecular water absorption polymer, reducing the ink absorption function. For example, when so-called edgeless image recording is performed in textile printing on cloth, sometimes ink adheres to a part, around the edges of the cloth, of the surface of the conveying belt. In this case, dye particles in the ink tend to accumulate in a corresponding part of the roller, and the absorption capability of this part drops relatively soon. This causes a problem requiring extremely frequent replacement of the roller and other components.
On the other hand, for such an apparatus, in order to avoid negative effects on the conveying accuracy of the conveying belt (see Patent Document 4), the blade wiper, the roller, and the like, are detached from the conveying belt during image recording, assuming cleaning of the conveying belt during non-recording time, such as prior to resuming of recording operation after occurrence of paper jam (see Patent Documents 1 through 3) or when cleaning is necessary (see Patent Document 4). However, in such a case as the above stated textile printing on cloth, image recording is often performed on a long cloth continuously for a long time, and if the conveying belt is left uncleaned during the image recording, ink continues to adhere to the conveying belt and stains the cloth as a recording medium. In such a way, ink is fixed on the conveying belt. Therefore, it is necessary to clean the conveying belt simultaneously while performing image recording on the cloth.
As an inkjet recording apparatus that performs cleaning of a conveying belt simultaneously during image recording, as described above, there is known an inkjet recording apparatus having a conveying device which cleans the conveying belt by removing ink deposited on the conveying belt by sandwiching the conveying belt between a guide roller, such as a tension roller, and a rotatable cleaning sponge in a roller form (for example, see Patent Document 5). In this apparatus, a dewatering belt is arranged downstream in the conveyance direction of the conveying belt with respect to the cleaning sponge so that the dewatering belt contacts the conveying belt to dewater the conveying belt. Or, an air blower is likewise arranged downstream of the conveying belt with respect to the cleaning sponge so that air is blown onto the conveying belt, thereby drying the conveying belt.
[Patent Document 1] Japan Patent No. 2705992
[Patent Document 2] Japan Patent No. 2891796
[Patent Document 3] Japan Patent No. 3016924
[Patent Document 4] TOKKAI No. 2000-272107
[Patent Document 5] TOKKAI No. 2003-205658
However, in the inkjet recording apparatus disclosed in Patent Document 5, a number of needle-shaped protrusions is provided on a conveying belt to anchor a recording medium relative to the conveying belt so that the recording medium cannot slide on the conveying belt. Therefore, the conveyance speed of the conveying belt and the surface linear speed of the cleaning sponge are necessarily the same. The cleaning sponge, herein, only absorbs ink on the conveying belt in a state of contact with the conveying belt, and cannot have relative motion that enables wiping off ink. Consequently, there have been some cases where ink on the surface of a belt is not removed well. Further, if the conveying belt is dried by a drying device, such as an air blower, downstream with respect to the cleaning sponge in a state that ink is not adequately removed from the conveying belt, solid portions such as dye are left on the conveying belt, causing subsequent problems in image recording. Still further, this apparatus has the drawback of requiring a large amount of consumption power for drying the conveying belt.
In order to wipe ink off a conveying belt with a cleaning sponge, it is necessary to provide a difference between the conveyance speed of the conveying belt and the surface linear speed of the cleaning sponge. However, if a speed difference is provided, friction from the cleaning sponge causes a load on conveyance of the conveying belt, which may have negative affects on the accuracy of conveyance of the recording medium by the conveying belt, as pointed out in Patent Document 4. Particularly, in the case where cleaning of a conveying belt and image recording are simultaneously performed as stated above, when the accuracy of conveyance of the conveying belt drops, irregularities will be generated in image recording on the recording medium. Accordingly, it is required to develop an inkjet recording apparatus having a cleaning device that features a cleaning performance capable of securely removing ink on the conveying belt and can clean the conveying belt without causing negative effects on conveyance accuracy.